Design of continuous-flow microwave reactor based on a leaky waveguide

Abstract

Using microwave heating for biodiesel production has several advantages, including an accelerated reaction rate and improved product quality. However, large-scale microwave-assisted biodiesel production still suffers from low efficiency and uneven heating, which limit its industrial applicability. To address these issues, in this study, a reactor based on leaky waveguide is proposed for continuous microwave-assisted biodiesel production. Firstly, a radiator based on a leaky waveguide is designed to realize a uniform distribution of microwave energy along the axial and longitudinal directions. Then, a multi-physics model based on electromagnetism, heat transfer in fluids, chemical engineering, and laminar flow is developed to simulate the continuous microwave-assisted biodiesel production process. Compared to the traditional bottom-fed and cylinder-fed reactors, the leaky-waveguide reactor has the potential to improve the heating uniformity and energy efficiency, and the microwave energy utilization efficiency can more than 95 % and the value of the outlet COV can be reduced to 1.51 × 10−3. Experiments were carried out to validate the proposed model, and the experimental results are in good agreement with the simulated results. Finally, the effects of the pitch circle radius, radius, and number of turns (screw pitch) of the helical tube used for the microwave-assisted biodiesel production process were analyzed. The radius and number of turns (screw pitch) have a greater effect on the system than pitch circle radius. This continuous microwave-assisted biodiesel production reactor provides a possibility for large-scale industrial production and can also be widely applied to the chemical engineering with pressure continuous flow reactor and food industry.